While this particular model is not described in either the 1885 or 1903 Seibert calatogs, it most likely conforms to the middle polarizing model IIb described in the 1903 catalog, but with the addition of the Bertrand lens. It features a substage polarizing condenser with a removable top element that is focused using a lever mechanism, an analyzing prism mounted in the tube in a slide-in holder, a centerable rotating stage with calibrations in degrees and venier, and a focusing slot which holds a Bertrand lens. An additional slot is provided that accomodates the compensator plates. Another, less complicated, polarizing microscope of similar vintage is also represented in the collection.